Compressive performance of innovative reinforced pillars in closed/abandoned mines

Abstract

Pillar is closely related to the stability and reliability of underground spaces in closed/abandoned mines. The present research introduced a new technique to strengthen square cement mortar columns via fiber-reinforced polymer (FRP) strips to verify the strengthening effect of FRP on pillars. Compared to a fully wrapped FRP jacket, the advantages of FRP strip are cost-effective and easy-to-construct. A series of compression tests as well as theoretical analysis were carried out to explore the mechanical behavior of square cement mortar specimens partially strengthened with FRP strips. The results verified the effectiveness of FRP strips in enhancing the stress and strain of cement mortar. Different from unconfined cement mortar specimens, these FRP-strengthened cement mortar specimens are featured with the double-peaked behaviors, mainly attributed to the stress state transformation from a one-dimensional to a three-dimensional stress state. It also indicated that the enhancement of stress increased with the FRP strip width. Moreover, the brittle-ductile transition ductile failure characteristics were also observed in FRP-confined cement mortar specimens. The ultimate ductility of the cement mortar specimen decreases gradually with the growth of the FRP strip width. The main contribution of this research is to enrich the strengthening techniques for residual pillars.

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